#include <iostream>
#include <iomanip>
#include <cmath>

double const pi = acos(-1);
double l1, l2, t;

int main()
{
	std::ios::sync_with_stdio(false);
	std::cin >> l1 >> l2 >> t;
	t = t * pi / 180.0;
	double d = (l1 + l2) / 2.0;
	double tmp = l1 * l1 / 4.0 + l2 * l2 / 4.0 - (l1 * l2) * cos(t) / 2.0;
	d += sqrt(tmp);
	d /= 2;
	double s = pi * d * d;
	std::cout << std::fixed << std::setprecision(10) << s << '\n';
}

